USB: ulpi: fix bus-node lookup

Fix bus-node lookup during registration, which ended up searching the whole
device tree depth-first starting at the parent (or grand parent) rather
than just matching on its children.

To make things worse, the parent (or grand-parent) node could end being
prematurely freed as well.

Fixes: ef6a7bcfb01c ("usb: ulpi: Support device discovery via DT")
Reported-by: Peter Robinson <[e-mail]>
Reported-by: Stephen Boyd <[e-mail]>
Cc: stable <[e-mail]> # 4.10
Signed-off-by: Johan Hovold <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/common/ulpi.c

···
 	/* Find a ulpi bus underneath the parent or the grandparent */
 	parent = ulpi->dev.parent;
 	if (parent->of_node)
-		np = of_find_node_by_name(parent->of_node, "ulpi");
+		np = of_get_child_by_name(parent->of_node, "ulpi");
 	else if (parent->parent && parent->parent->of_node)
-		np = of_find_node_by_name(parent->parent->of_node, "ulpi");
+		np = of_get_child_by_name(parent->parent->of_node, "ulpi");
 	if (!np)
 		return 0;